Light emitting diode (LED) lamps have been developed to replace conventional incandescent or fluorescent lamps for reducing electrical and maintenance costs, and for increasing reliability. LED lamps consume less electrical energy than conventional lamps while exhibiting much longer lifetimes. Such LED lamps typically include a power supply and a plurality of LEDs mounted on a flat or curved surface.
One growing use of LED lamps is the replacement of incandescent light bulbs in traffic signal lamps. A common conventional traffic signal lamp is illustrated in FIGS. 1 and 2, and includes a housing 1, a front door plate 2, a lens 3, a reflector 4 and an incandescent light bulb 5. Retainers 6 affix the lens 3 to the front door plate 2, which opens via hinges 7 to allow access to the interior of the housing 1. Light bulb 5 screws into electrical socket 8, which is electrically attached to a terminal strip 9, which in turn receives its power from the traffic signal controller.
It is known to replace the incandescent light bulb 5 with an LED lamp, along with the lens 3 since it is designed for the output of an incandescent light bulb. In a conventional traffic signal lamp retrofit procedure, the lens 3, light bulb 5, reflector 4 and socket 8 are all removed, and an LED lamp module 10 is installed to the front door plate 2 to replace lens 3, as illustrated in FIG. 2. Wires 11 from the LED lamp module are connected to the terminal strip 9.
The above mentioned retrofit method has several drawbacks. First, it is time consuming and labor intensive to remove the reflector 4 and socket 8, and access the terminal strip 9 with new wiring. Because traffic is usually blocked in order to access traffic lights, time is of the essence. Second, in order to safely disconnect the socket connector wires from the terminal strip, and connect new wires from the LED lamp module 10 to the terminal strip, the power to the traffic signal must be temporarily turned off, which disrupts traffic flow through the intersection. Finally, once the retrofit is complete, it is not possible to put the original incandescent lamp back in the traffic signal lamp, for example in case a spare LED lamp is not available.
There is a need for an LED lamp and retrofit procedure for traffic signal lamps that is fast, simple, requires minimal labor to install, does not require turning the power off to the traffic signal, and allows reinstallation of the original incandescent lamp.